The impact of COVID-19 lockdown on surface air quality changes in major African countries

Abstract. The lockdown during the coronavirus disease 2019 (COVID-19) pandemic provides a natural experience to examine the air quality changes from emission reductions. However, limited monitoring data has made it challenging to study these changes in major African regions. This study aimed to assess air quality changes, including major pollutants such as CO, NO₂, O₃, SO₂, and aerosol particles during COVID-19 lockdowns in 2020 across different African countries. Using chemical reanalysis products from the Jet Propulsion Laboratory, we calculated quarterly dual anomalies and quarterly anomalies for MAM (March to May) and JJA (June to August) in 2020. Results showed a general decline in CO, NO₂, O₃, and nitrate aerosol across majority African countries, with more pronounced decreases during JJA. However, discrepancies were also seen: quarterly dual anomalies revealed a decrease in NO₂ and SO₂ in Northern Africa (NA), while quarterly anomalies showed an increase, suggesting containment policies moderated the increase rates. In Southern Africa (SA), both methods observed increases in SO₂, likely due to relaxed restrictions and heightened energy demands. Sensitivity diagnostics showed that the increase in O₃ in South Africa may be related to the decrease in NO₂. Additionally, increased in sulfate and ammonium aerosols in NA and SA was likely attributed to dust events and higher residential emissions, respectively. For this study, we concluded that air quality changes may be intertwined with both natural and anthropogenic influences and the results highlight the necessity for stricter emission standards for coal-fired plants and promote clean energy in African countries.